The present invention relates to an apparatus for evaluating a liquid hydrocarbon to determine the propensity for coke formation and in particular to an apparatus for evaluating lubricant, or oil, to determine the propensity for coke formation.
In a prior art apparatus for evaluating a lubricant or oil, to determine the propensity for coke formation, the apparatus comprises a supply of oil, lubricant, in a reservoir and a heater to heat the oil in the reservoir. A supply of air is arranged to supply air into the oil in the reservoir such that the air is bubbled through the oil. The reservoir is arranged to supply the air to a vertical test pipe and a heater is provided to heat the test pipe. A thermocouple is arranged to measure the temperature of the oil in the reservoir. The mass, weight, of the deposit on the test pipe is used to give a measure of the propensity for coke formation.
However, the air flow through the test pipe contains a fraction of oil vapour and forms deposits, coke, on the test pipe. Thus, a first problem with this apparatus is that the evaluation only determines the propensity for coke formation for a fraction of the oil and not the fully formulated oil. A second problem with this apparatus is that the evaluation only determines the propensity for coke formation for a vertical test pipe.